TS 1449 

.H4 

1916 

Copy 1 Eighth Series, No. 5 



November 4. 1916 



ol^arlf^rfi OlnlUg^ lullrtm 




The Determination of Cotton 
and Linen 

By Physical, Chemical and Microscopic Methods 

BY 

ALOIS HERZOG. Ph.D. 

Director of Department of Fla.>: Culture, Prussian Higher Technical School 
for the Textile Industry, Sorau, N. L. 

TRANSLATED FROM THE SECOND EDITION BY 

ELLEN BEERS McGOWAN 
Instructor in Household Arts, Teachers College 



Technical Education Bullatln, No. 7 
PRICE. 25 CENTS 



Published by 

iLeatifna (Hallt^e, Qlolumbia MniufrsUg 

525 West 120th Street 
New York City 






iStaiiitrB (CoUpgr liiillfttn 

Published fortnightly from September to May Inclusive. Entered as 
second class matter January 15, 1910, at the Post OfCice at New Tork, 
New York, under the Act of August 24, 1912. 



M.9.21. 



1 



Eighth Series. No. 5 November 4, 1916 

S^arlf^rs (ttallrgr lull^tm 




The Determination of Cotton 
and Linen 

By Physical, Chemical and Microscopic Methods 

BY 

ALOIS HERZOG, Ph.D. 

Director of Department of Flax Culture. Prussian Higher Technical School 
for the Textile Industry, Sornii, N. L. 

TRANSLATED FROM THE SECOND EDITION BY 

ELLEN BEERS McGOWAN 

Instructor in Household Arts, Teachers College 



Technical Fducation Bulletin, No. 7 
PRICE, 25 CENTS 



Published by 

Srarlirra (Jlnllrgr. (Enlumbia Uniupraittj 

525 West 120th Street 
New York Ctty 



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INTRODUCTION 

This pamphlet, a translation of Professor Herzog's "Die 
Unterscheidung von Baumwolle und Leinen,"^ is oflfered as a use- 
ful handbook for persons concerned with textile manufacture, in- 
struction, and especially textile purchase and use. Textiles have 
become a subject of importance to the purchaser since household 
manufacture has passed by with its intimate acquaintance on the 
part of maker and user with the characteristics and values of dif- 
ferent fibres and fabrics, and in its stead has come the situation of 
purchaser on one side the counter, and sales-person on the other, 
both equally ignorant of textile values, often of textile identity. 
But sales-people on their part are trying to increase their knowl- 
edge : the instruction in salesmanship which has been organized in 
many places gives textiles its proper place in the curriculum. 
Schools of household arts and college departments of home eco- 
nomics have for several years recognized the necessity of textile 
study to educate the consumer. But there has been a dearth of 
scientific material available. The schools of textile technology all 
give instruction in textile chemistry and other applied science nec- 
essary to equip the successful manufacturer, or the producer, of 
textile goods. If we may believe the cynics, such schools indeed 
train the producer in shrewder methods and darker matters than 
the consumer may ever hope to unravel or bring to light. Fairly 
judged, however, modern textile manufacture where it has been 
criticized has simply devised ways of producing expensive effects 
with cheap materials, as mercerizing cotton to make it look like 
silk, and weighting actual silk with tin salts to give what seems 
heavy silk at costs far below pure silk. Such attempts go wrong 
when either the customer buys ignorantly and laments afterward, 
or when the manufacturer actually overshoots the mark in his en- 
deavor to produce cheap but attractive goods and produces defec- 
tive ones with a low wearing efficiency. We none of us desire to 
go back to unbleached muslin and butternut gray, but we have a 
right- to demand a dollar's worth of wear as well a dollar's worth 
of efifect from our clothes. 



I Verlag fiir Textile-Tndustrie, Berlin, S. W. 



INTRODUCTION 

The remedy is more science — more for the manufacturer, 
more for the consumer. Good bridges are built for stress and strain 
as well as beauty. We ask as much of our textile fabrics. The 
United States Army examines for tensile strength, fastness of dye, 
and trueness of fibre, every roll of cloth, consignment of men's 
hose, etc., that clothes the soldier. Progress for lis all will come, 
it seems likely, through an honest system of labelling, so that, for 
example, cotton blankets will not by a "trade custom" be labelled 
"all wool," as was done in one of New York's best stores a year or 
so ago ; perhaps "standards" or definite grades can be established 
in certain lines ; possibly the suggested Federal legislation for pure 
textiles, comparable to pure food legislation, will bear fruit. But 
at any rate progress is certain — we cannot permit hospitals and 
large institutions to administer the budget item of hundreds, per- 
haps thousands of dollars for linens and textiles upon a basis of 
rule-of-thumb and ignorance, nor will the individual forever bear 
being hood-winked with textile mixtures when he wishes and is 
willing to pay for pure goods, whether in wool, in linen, or in silk. 
Health and the pocketbook — a strong combination — are both con- 
cerned. The same degree of publicity that has been secured for 
food manufacture is asked — and this knowledge will save the situ- 
ation for producer and consumer alike. 

The translation of Professor Herzog's little brochure has been 
faithfully made by Ellen Beers McGowan, instructor in household 
arts, Teachers College. The methods which it outlines have been 
used in the course in textiles in the School of Practical Arts. It 
is hoped that this translation may be useful in other institutions, 
and to individuals concerned with textiles, whether in manu- 
facture, sale, or purchase. 

Cordial acknowledgment is to be made to the author. Pro- 
fessor Herzog, Director of the Department of Flax-Culture in the 
Prussian Higher Textile School of Sorau, for permission to make 
the translation, and to his publishers, der Verlag fiir Textile In- 
dustrie of Berlin, for making available the illustrations. 

Benjamin R. Andrews 

Assistant Professor of Household Arts, 
Teachers College, Columbia University 
August, IQII 



AUTHOR'S PREFACE 

During my practical work in the linen industry, I had ample 
opportunity to observe what great commercial and technical im- 
portance attaches to the distinction between flax and cotton fibres. 
Unfortunately, I was obliged equally often to notice that the 
knowledge of the distinguishing marks has not penetrated to a 
very wide circle, and indeed that the judgment of many engaged 
in the textile industry is unreliable as soon as it comes to a 
question of tests of material of unknown origin or of cotton goods 
which on account of dressing look like linen. 

In this publication, now in its se^-ond and essentially enlarged 
edition, I have considered especially the methods of testing which 
it is possible for everybody to carry out quickly and without com- 
plicated apparatus. Of course I was obliged to mention also the 
most important method of identifying both fibres — the microscopic 
test, which gives unquestioned scientific results. The somewhat 
more detailed handling of this subject here as compared with the 
first edition, will be, I hope, to many not unwelcome. 

The special value of this entirely practical pamphlet was the 
introduction of original photographs, which would enable one en- 
tirely unskilled, by carefully comparing them with specimens pre- 
pared for the microscope, to gain the desired result. The larger 
number of illustrations in this second edition should therefore in- 
crease the practical usefulness of the pamphlet. 

A. Herzog. 

Sorau, N. L., March, ipo8. 



The Determination c^ Cotton and Linen 

I. Simple Physical and Chemical Differences Between 
Cotton and Linen 

In view of the great difference in price between bleached Hnen 
and cotton materials, it is not surprising that for some time simple 
methods of recognition of the fibres named have come into use, 
based partly on physical and partly on chemical differences. 
Although many of these "tests" allow great latitude for indi- 
vidual judgment, so that they are not always scientifically con- 
clusive, it is undeniable that some, for instance the oil test, give 
good results in skilled hands. Although in general I agree with 
Wiesner that for technical practice scientific methods of examina- 
tion should alone be authoritative, I hold that in the present case 
it is going too far to reject, as empirical, certain physical and 
chemical identification tests for linen and cotton, since by their 
help good results may be obtained with a minimum of time and ap- 
paratus. Upon like grounds the technical chemist would be obliged 
to discard many very useful tests, as the blowpipe test, color reac- 
tions with oils, breaking test for metals, etc., although these are 
entirely satisfactory as preliminary tests in the laboratory and in 
the management of manufacturing establishments. 

As preliminary working tests the following methods of dis- 
tinguishing between cotton and linen should be considered. Many 
of them (as the oil test) are of great importance in microscope 
work, as for example when it is a question of the presence oi 
cotton threads in a linen weave. In this case it would cause loss of 
time if one should use the microscope to distinguish all the threads. 
As experience shows, it is amply sufficient to test with the micro- 
scope only those threads which appeared doubtful in the prelimi- 
nary examination. 

A. Physical Tests 
1. Tearing Test. 

In general linen weaves are more difficult to tear than cotton. 
The torn ends of linen appear unequal in length, parallel fibred, 
and glossy. Cotton shows curling, lustreless threads of almost 
equal length. (See Figs. 1 and 2.) 



PHYSICAL AND CHEMICAL DIFFERENCES 




■^ig. 2. Torn end of linen material. Mag. 8x, 



8 



DETERMINATION OF COTTON AND LINEN 



With practice it is possible to distinguish between the sounds 
resulting from tearing the material: — Linen, shrill; cotton, dull 
or muMcd. If yarn is broken quickly, cotton fibres will curl, while 
linen fibres remain stretched. 

2. Untwisting Test. 

Cotton threads are made up of a number of fibres so niter- 
wo- '''in- thev show different directions in each 




Fig. 3. Untwisted linen yarn — three threads at right ; and cotton 
yarn — three threads at left. Mag. 8x. 



PHYSICAL AND CHEMICAL TESTS y 

turn of the fibre, while linen threads similarly handled show a 
more or less parallel arrangement of the glossv individual fibres. 
(See Fig. 3.) 

3. Light Test. 

On examination of material held against the light (or in re- 
fracted light), flax fibres appear strikingly streaked or uneven, 
while cotton fibres are marked by great uniformity. (See Fig. 4.) 
The streaking in the former case is always present in the flax 
yarns (linen and tow) and is technically attributable to unavoid- 
able inequalities in the thickness of the threads. 




Fig. 4. Half-linen goods examined against the light. The linen 
threads are marked by knotty places. Mag. 4X. 



4. Singeing Test. (Stockhardt). 

Burned ends of linen threads, after the flame is extinguished, 
appear scorched in an even, compact manner, while cotton threads 
similarly treated spread apart more or less like a paint brush. 
(Fig. 5.) 



10 



DETER JIINATION OF COTTON AND LINEN 




Fig. 5. Singed cotton threads at left and linen threads at right. 
Mag. lox. 



5. Oil Test. (Frankenstein). 

This test, in a somewhat modified manner, is carried out as 
follows : The piece of goods, freed from dressing by boiling out 
in water or warm soda solution, is laid on a glass plate, saturated 
with fatty oil, and, avoiding air bubbles, covered with a smaller 
glass plate. After the removal of the surplus oil from the edges 
of the cover glass, the sample is examined, first against the light, 
then with the light falling on the object. The linen fibre because 
of its thick cell wall, which approaches the refractive index of the 
oil, assumes a transparent appearance, like a grease spot on paper; 
i. e., it appears clear against the light, and dark when light falls 
upon it. The opposite effect is noticed in cotton. Hence the lat- 
ter appears bright with the light falling upon it, and dark against 
the light, not only because the air in the relatively thin-walled cell 
of the lumen is not replaced by the oil, but also because the air 
bubbles between the separate intertwisted fibres give an opaque 
appearance. This is especially noticeable tmder the low power of 
the microscope. (Fig. 8; and also 6 and 7.) 

This test gains by contrast, when combined with the follow- 
ing methylen-blue test, recommended by Behrens ; or with the' 
copper-sulphate-potassium-ferrocyanide method proposed by the 
author. 

The above mentioned oil test, and also the following tests, 
are carried out with small square fringed pieces of goods. With 
all methods a good microscope should be constancy used. 



PHYSICAL AND CHEMICAL TESTS 



11 




Fig. 6. Half-linen subjected to oil test. Appearance with light 

falling upon it. In the illustration the cotton threads are 

vertical, the linen horizontal. Mag. 8x. 




Fig. 7. Half-linen subjected to ,oil test. Appearance against the 
light. Cotton threads vertical, linen horizontal. Mag. 8x. 



12 



DETERMINATION OF COTTON AND LINEN 



B. Chemical Tests 

6. Sulphuric Acid Test. (Kindt and Lelinert). 

The dressing-free, air-dry material is immersed from one to 
two minutes in concentrated sulphuric acid ; next, well washed in 
water, and then dried between filter paper. Cotton under this 
treatment will dissolve almost completely ; linen remains nearly 
unaffected. (Fig. 9.) This method of identification, available 
also for colored goods, is often employed to get an approximate 
quantitative estimate of half-linen goods. (Method of dififeren- 
tiation). 




Fig. 8. Illustration of half-liiien union goods oiled. Fibres run as 
in preceding illustration. Mag. 25X. 



C. Dyeing Methods 

The useful color tests for distinguishing cotton and linen fall 
into three groups. The first has for its basis the different absorp- 
tive power of both fibres for metallic salts ; the second has refer- 
ence to the slight chemical difference between the cell walls of cot- 
ton and flax fibres; and the third limits itself almost exclusively to 



PHYSICAL AND CHEMICAL TESTS 



13 





■'■ Till 






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Fig. g. Half-linen goods subjected to sulphuric acid test. Linen 
remains ; cotton is almost entirely dissolved. Mag. 4x. 

this fact — that the accompanying constituents of the flax fibre, 
namely epidermis and bark cells, which are rarelv absent, are 
made especially prominent by appropriate dyes. 



Group I: .-Ibsorptioii Differences. 

7. The author's copper sulphate and potassium ferrocyanide 
method is best adapted to this purpose. Although cotton dipped 
in a weak copper sulphate solution may retain appreciable quanti- 
ties of copper salts, one can not succeed in proving these clearly in 
the fibre by means of potassium ferrocyanide. It is otherwise with 
the flax fibre, which absorbs approximately twice as much copper 
salts. The practical application of the test is as follows: A small 
piece of fringed material, free from dressing, is laid for ten 
minutes in a copper sulphate solution of a suitable strength, 10 
per cent, and then washed under the faucet, to remove the adher- 
ing surplus of copper salt. Thus washed, the material is then 
placed in a 10 per cent solution of potassium ferrocyanide. If the 
material is half linen there appears in the part which consists of 
flax fibre (warp or woof) a striking copper-red color, due to the 
separation of ferrocyanide of copper; while the cotton fibres re- 
main uncolored. Watch glasses may be employed for the experi- 



14 DETERMINATION OF COTTON AND LINEN 

tnent. Beautiful results can be secured, if the above-treated piece 
of material is washed in water, and after thorough drying is en- 
closed in Canada balsam, in the same manner in which a slide is 
prepared for the microscope. In place of the Canada balsam a 
fatty oil may be used. As may be seen conclusively with the mi- 
croscope, the coloring shown by the flax fibres is to be attributed 
not merely to the accompanying constituents, but is peculiar to 
the fibres. This detail is of especial analytical value in the e\am- 
ination of the finest linen batiste, which in certain circumstances 
is without the accompanying constituents. As microscopic exami- 
nation shows, the difference in the coloring of the fibres and their 
accompaniments is to be noticed only to the extent that the former 
seems colored more of a copper-red, the latter more of a brick-red. 
The difference in the colors, especially after lying in Canada bal- 
sam, is more marked than in any of the other microscopic color 
tests known at present. Therefore the method just described may 
be especially recommended. The tests in which balsam is used are 
especially adapted to demonstration purposes. 

Group II: Chemical Differences. 

8. As a representative of this group, Behrens's methylen-blue 
test is here introduced. A small piece of woven material is col- 
ored in a warm solution of methylen-blue, and then washed thor- 
oughly. On repeated washing it will be found that the coloring 
matter will almost entirely come out of the cotton, while in the 
same time the flax fibre appears colored a clear blue. In an earlier 
stage the cotton fibre appears a green-blue, different from the color 
of the flax. The distinction is especially noticeable by yellow 
lamplight. This test, like the one before mentioned, may be com- 
bined with the oil test. (See Fig. 10.) 

At this point one detail should be noted. Although this 
method yields favorable results with correctly bleached flax and 
cotton fibres, it is uncertain as soon as fibres are used, which in 
the bleaching have undergone undesirable chemical changes (a 
change of cellulose into oxycellulose). According to investiga- 
tions by Witz and others, the fibre substance, changed in part or 
wholly to oxycellulose, shows an especial affinity for methylen- 
blue. Therefore, in a half-linen weave containing improperly 



PHYSICAL AND CHEMICAL TESTS 



15 




Fifl;. 10. Half-liiien. Mag. 4.x. Color test witli methylen-blue. 
Liren fihm, dark-blue ; cotton. liglit-blue. 




Same as Fig. 10 

Fig. II. Half-Iiiien. 4.K mag. Color test with fuchsine and am- 
monia. Linen fibre red; cotton, white. 



16 DETERMINATION OF COTTON AND LINEN 

bleached cotton, the latter will hold the methylen-blue color even 
more firmly than the flax fibres. As it is not possible for the lay- 
man, without further instruction, to decide whether or not the un- 
desirable change in the fibre substance has taken place, only a 
limited value attaches to the above method of examination. 

9. Behrens has proposed other similar dyeing tests, e. g., 
with safranine, Bismarck brown, etc. Since with their help no 
better results are reached than with the methylen-blue dye, a 
special description of them is omitted. 

Group III : Constituent Parts. 

According to the older methods of this group alcoholic solu- 
tions (tinctures) of different natural dyestuffs were allowed to 
act upon the weave under examination. After about fifteen min- 
utes the material is taken out of the dye, dried superficially 
between filter paper, and observed in moist condition. The result 
with madder and cochineal tinctures is as follows : 

Linen. Cotton. 

10. Madder tincture: orange pale yelloiv 

11. Cochineal tincture : violet pink 

Much better contrasts are obtained with Bottger's fuchsine or 
Herzog's cyanin test. 

12. In Bottger's fuchsine test the weave is laid in a neutral 
alcoholic fuchsine solution for some minutes ; then washed in 
water and laid in concentrated ammonia. The fuchsine dye will 
almost entirely leave the cotton, while in the impure flax fibre it 
remains a long time, though quite faded (rose colored). (See 
Fig. 11.) 

13. The cyanin test given by the author is made as follows: 
A small square piece is cut from the weave to be examined, and 
fringed out. It is then laid for some minutes in a lukewarm alco- 
holic solution of cyanin (obtainable from Griibler & Co., Leipzig). 
After the resulting absorption of the dye, it is washed in water 
and then treated with diluted sulphuric acid. This efifects a com- 
plete removal of color from cotton goods, while flax fibres in the 
same time show a clear blue color. This color is prominent in the 



PHYSICAL AND CHEMICAL TESTS \J 

epidermis cells (especially the cuticle part), found in the ilax fibre, 
since these seize upon the cyanin dye with avidity. To intensify 
the blue coloring it is recommended that the fibre, so treated with 
sulphuric acid, be thoroughly washed and placed in ammonia. The 
dye then appears to be substantially fixed in the flax. 

Supplementary Tests 

14. In conclusion, attention may be called to the fact that 
equally thick linen and cotton goods exhibit considerable differ- 
ence in weight. According to K. B. Lehmann, linen goods of 
equal volume are about 1" per cent heavier. This fact, based upon 
the structural characteristics of both fibres, and their way of lying 
in the weave, should however be used only after much practice, 
and then with prudence, as a means of differentiation. 

15. Cotton materials feel warmer than linen. The investi- 
gations by Rubner allow the conclusion that cotton by its peculiar 
structure makes the circulation of air difficult, and holds the heat 
more than linen goods of the same thickness. (From 15 to 30 per 
cent more.) 

Mercerized Cotton 

i6. Mercerized cotton, so much used at present, is of recent 
discovery. It is obtained by treating ordinary cotton with strong 
sodium hydroxide solution with a simultaneous stretching of the 
fibres. It is characterized by a high lustre, almost like silk, and 
may be easily recognized by Lange's method. That is, if the cot- 
ton material is immersed in an iodine-saturated, concentrated so- 
lution of zinc chloride iodide, it is colored an intense blue. This 
color is easily removed from ordinary cotton by washing in water, 
while it remains fixed in the mercerized fibre. In the practical 
application of this test, also in the case of colored goods, any pos- 
sible starch present in the dressing must be removed by long 
boiling in water. 

17. Another method for the recognition of mercerized cot- 
ton has been suggested by Mr. David. It rests upon the fact that a 
fibre mercerized for the second time slum's after this treatment no 
further affinity for dye stuffs. The thread or weave to be tested, 
if it is colored, is faded out as much as possible (e. g. with hydro- 
chloric acid) and stretched on a frame. Then three solutions of 
sodium hvdroxide are prepared: 1, a solution of 40° Be; 2, one of 



18 DETEkMlNAtlON OF COTTON AND LINEN 

40° Be diluted with an equal volume of water ; 3, one diluted with 
three parts of water. The material stretched in the frame is now 
touched in different places along the stretched edge with these 
solutions. After a time the frame is dipped in water in order to 
wash out the sodium hydroxide, then acidified and again washed. 
Then follows coloring with a dye stuff, for instance, Congo red. 
If the weave so treated has not previously been mercerized, the 
touched places will take a considerably more intense color than 
the untouched part of the fabric. But mercerized fabrics show no 
difference in coloring. 

i8. For other means of distinguishing ordinary and mercer- 
ized cotton, we turn to the microscope. This is also effectual in 
recognizing silk finish and crepe finish. 

II. Microscopic Tests 

It should be pointed out concerning the foregoing, that many 
of the tests described may fail under special circumstances. This 
is readily understood, when it is remembered that in both raw 
products there is the same chemical substance, namely cellulose. 
With the lack of essential chemical differences, attention must be 
given to the foreign ingredients of the fibres, attendant on their 
production (the epidermis of the flax stalk, woody parts, etc.,) or 
to the morphological differences. The latter find their visible ex- 
pression in the form of the fibres. Considering- the extraordinary 
fineness of the cells composing the fibres it is apparent that a com- 
pound microscope is necessary for their examination. 

The differences in structure, as shown by the microscope, are 
so constant and characteristic that they entirely exclude the pos- 
sibility of an error in the diagnosis. Therefore the oreatest im- 
portance should be ascribed to the tests zvith the microscope, and 
its use is recommended in all cases where an absolutely certain de- 
termination must be reached. With the present low price of mi- 
croscopes the necessary expense to anyone buying textiles in 
quantity would soon pay for itself. The optical firm of E. Leitz 
in Wetzlar, Germany, has a small microscope on the market, 
which considering its low price and superior optical qualities, 
seems to me especially adapted to the foregoing purpose. Before 
buying instruments of lesser worth, cried up by various firms, one 
" cannot be too strongly warned that they are useless for our pur- 



MICROSCOPIC TESTS 



19 



pose. But on the other hand expensive and comphcated instru- 
ments are not to be reconiniended since they are often constructed 
too deUcately, and moreover lack the handy quahty one needs for 
technical purposes. I have satisfied myself that the above men- 
tioned instrument by Leitz meets all reasonable demands in a 
satisfactory manner. Moreover it is solidly built and enclosed in 
a small case, so that it is portable. It is, in short, most suitable 
for fibre identification tests. 

When one considers that only a brief time is required both for 
the preparation and actual microscopic examination, and that a 
minimum of material is requisite, which is of great importance in 
testing patterns or samples which cannot be cut or otherwise 




Fig. 12. Egyptian raw cotton shown under the microscope. Typical. 



20 



DETERMINATION OF COTTON AND LINEN 



damaged, one can only express surprise that so little use is made 
of the microscopic method, so absolutely exact and so free from 
objections. 

Cotton 

Technically, cotton — unicellular and wooly-seeded — belongs 
to the Gossypium division (mallow family). The hairs are nar- 
rower at the base than in the middle, and measure 12-42 /; ( 1 ;< = 
0.001 mm.) in breadth, and 10-50 mm. in length (Wiesner). The 
cell wall is strongly developed and enfolded in an extraordi- 
narily thin, granular or striped skin — the cuticle. It is 
twisted occasionally, more seldom in its whole length, like a cork- 
screw, and the stronger and more uniform the twisting, the better 
the quality (Hanausek and Herbig). On account of the peculiar 
shape of the cross section (reniform) the hollow fibre in the longi- 
tudinal view seems defined by calling it roll-shaped. The hair is 
closed at only one end. (See Fig. 12.) 




Fig. 13. Microscopic appearance of dead cotton. 



MICROSCOPIC TESTS 21 

The fibre is entirely free from wood, and therefore shows after 
treatment with zinc chloride iodide a clear cellulose reaction 
(red violet). The cross sections are elliptical to kidney-shaped, 
less frequently almost circular in the best kinds, with short colum- 
nar lumen. Cotton sliozvs characteristic modification after treat- 
ment zvith ammoniacal copper oxide. However, it should be said 
that not all kinds of cotton give this appearance, just as that also 
many bast fibres yield an analogous swelled appearance. 

With this treatment the cotton fibre swells up in blistered or 
barrel-shaped manner, until finally almost the last fragments of 
the cuticle and the inner skin with its traces of protoplasm, fully 
dissolve. The cuticle, which is not capable of swelling, is found 
on the outside of the fibre, in the form of shreds or a ring-like lac- 
ing. (See Fig. 23, page 30). A similar if somewhat less pro- 
nounced appearance results after treatment with iodine and di- 
luted sulphuric acid. 

With certain varieties will be found very weak-walled, slight- 
ly twisted fibres of dead and unripe cotton, with frequent double 
striping. It follows that their tendency to take dyestufifs to only 
a limited extent should be taken into account in the examination of 
colored goods of inferior quality. (See Fig. 13.) 

Accurate identification of particular sorts of cotton is accom- 
plished only with much difficulty ; it is based on the measurement 
of the maximum breadth of hair most often appearing. 

Cotton shows strong double refraction. Between crossed 
Nicols the fibres appear in polarization colors, first order (mostly 
yellowish), only in those places where they turn their narrower 
side (turning places) up. Colors of the second and higher order 
also appear. With parallel Nicols the corresponding complemen- 
tary colors of the crossed position appear. 

By such a method of examination, which naturally is possible 
only with a polarization apparatus, all inequalities and rough- 
nesses of the fibre are apparent. 

Cotton fibres colored with Congo-red in contradistinction to 
flax, appear only faintly dichroic. (Behrens.) 

For distinguishing the hues of flax and cotton, the double col- 
oring with safraninc and chrysophen was proposed bv Behrens. 
On account of the minor importance of these methods they will 
not be discussed here. 



22 



DETERMINATION OF COTTON AND LINEN 



Mercerized Cotton 

Under the microscope, the mercerized cotton of Mercer, also 
that of Thomas and Prevost (under tension), can easily be dis- 
tinguished from the unmercerized. The former appears more or 
less stretched and smooth on the surface. The lumen of these 
cylindrically-shaped fibres shows, in different places, astonishing 
shrinkage and enlargements — many times it is scarcely visible. 
Internal granular fragments are often found. Steeped in ammon- 
iacal copper oxide, the mercerized fibre swells quickly, so that 
almost the last trace of the inner skin dissolves. Peculiar forms 
of swelling are, however, not observed. After application of zinc 
chloride iodide, the fibre is colored amore intensely than ordinary 
cotton. The transverse section shows a nearly circular form. As 
has already been suggested above, the directions given by. Lange 
can be applied well to the microscopic investigation. 

Silk Finish 

In this place the tests of so-called silk — or ripple — calendered 
finish should be briefly considered. The beautiful and silk-like 
lustre which is lent to cotton goods (for the most part mercerized) 
by the silk finish, is produced by numerous very fine parallel press 
lines or ribs. These ribs are easily detected by placing a piece of 




Fig. 14. Microscopic appearance of mercerized cotton. Mag. 15OX. 



MICROSCOPIC TESTS Li 

the material under the lowest power of the microscope, and turn- 
ing it backward and forward. It is better in this case to remove 
the selvage of the weave and look for press lines on the remaining 
prominent fibres. (See Fig. 15.) Similar effects are produced 
nowadays in the popular crepe material, although with the differ- 
ence that the press lines follow a definite pattern. 




Fig. 15. Silk-finished calendered mercerized cotton. As shown in 
a magnifying glass. 



24 



DETERMINATION OF COTTON AND LINEN 



Flax Fibre 

The raw or unspun, unbleached flax fibre consists of numer- 
ous, united, bundle-forming primary bast fibres. The breaking- 
down of a fibre bundle into its constituent parts begins under the 
chemical influence of bleaching. For this reason if we are pro- 
ceeding to study raw fibre, we must first open up the bundle by 
boiling the flax with a caustic soda solution (about 10 per cent). 
With bleached fibres this preliminary treatment is not necessary. 

The elementary bast fibres, according to the part of the stalk 
from which they are taken, show important dififerences in their 




Fig. l6. Microscopic appearance of tiax fibre in zinc chloride 
iodide. Mag. loox. 



microscopic structure. Then, too, characteristics of species and 
practices of culture (in particular the time of harvesting the flax), 
and other circumstances, bring about differences in the fibres 
which cannot be overlooked. The vast majority of fibres exhibit 
the following structure : — The primary fibers are arranged in 
groups and show sharply polygonal cross-sections. The cell wall 
is so strongly thickened that the enclosed lumen appears thread- 
like in the longitudinal view. The lumen is almost filled with 
dried particles of albumen. (See Fig. 16). In bleached 



MICROSCOPIC TESTS 25 




Fig. 17. Flax fibre in olive oil. Mag. ioo.k. 
fibres the albumen ingredient may be lacking to a great extent. 
With zinc chloride iodide the cell walls are colored red violet, 
while the traces of albumen in the lumen take a yellow brown 
color. 

In general the fibres are very uniform ; they measure 21 u 
transversely. Both fibre ends run to a sharp point. The cell wall 
always shows a mechanical deformation of transverse knotty 
swellings, so-called displacements. These are especially promi- 
nent after treatment with zinc chloride iodide or fatty oil. (See 
Figs. 17, 18, and 19). The polariscope also gives excellent ser- 
vice in making them visible. 

For manufacture of permanent specimens a coloring with saf- 
ranine, according to my experience, answers very well. After 
fibres which have been well washed and thoroughly dried are en- 
closed in Canada balsam, the albumen-filled canal differentiates 
itself from the light red cell wall by its dark red color. The same 
methods may be employed for the observation of dichroism. 

Another important microscopic test shows the fibres of the 
so-called root end of the flax stalk (the lower part of the flax 
stalk). 

On account of the weakness of these fibres they offer little 
resistance to the vigorous mechanical preparation that they under- 
go, and in this way cause for the most part the fibre waste (tow). 



26 



DETERMINATION OF COTTON AND LINEN 




Fig. i8. Typical appearance of flax fibre from the middle of the 
stalk, in zinc chloride iodide. Fine fiber with clearly 
defined cell canal (filled with remains of albumen) and 
characteristic displacements. Mag. 40OX. 

They are therefore very frequently met with in tow-spun material. 
In longitudinal view, fibres from this part of the stalk appear very 
Battened, broad, and clearly stratified. (See Figs. 19, 20). The 
stripings are always observable. The cell ends are mostly rounded 
off. Zinc chloride iodide gives a red-violet color, occasionally 
muddy-greenish. The sound, intact fibre measures S2u trans- 
versely. An exhaustive description of the morphological charac- 
teristics of the different parts of the stalk does not come within 
the scope of this pamphlet. 



MICROSCOI'lC TliSTS 



27 



The flax fibre always shows a very strong specific double 
refraction. Observed between crossed Nicols, it appears uni- 




Fig. 19. Typical appearance of tlax root in zinc chloride iodide. 
Coarse fibre with wide lumen and small granular frag- 
ments of protoplasm. Cross markings — displacements — 
noticeably large. Mag. 40OX. 



formly colored in its greater extent. The predominant color is 
violet. The vivid polarization colors pass to the yellow, second 
order. The clearest results are obtained when the fibres are en- 
closed in a medium, the refractive index of which is very nearly 
identical with that of cellulose (Canada balsam or sodium salicy- 
late). Flax fibres colored with Cong^o-red are strongly dichroic 



28 



DETERMlNA'l ION UK COTTON AND LINEN 



(Behrens). By the backward and forward turning of the colored 
specimen on the object-stand, under wliich a Nicol has been in- 
serted, the primary fibres are alternately intensely red and nearly 
colorless. Dichroism may also be observed after treating with 
zinc chloride iodide. With the exception of the macerated fibres 
from the root ends, which show deviations, the following phc- 
nouicna may he observed after putting flax fibres in freshly pre- 
pared ammoniacal copper oxide: the cell wall shrinks, as Wiesner 
has pointed out, and dissolves under the appearance of a longitudi- 




Fig. 20. Typical bast fibers from the lower part of the flax stalk, 
in chloride zinc iodide. Rather coarse fibre with clearly 
visible canal filled with traces of albumen. Longitudinal 
stripes apparent. Mag. 400X. 



MICROSCOPIC TESTS 29 

nal striping corresponding to tlie secondary thickened layers. At 
the same time the protoplasmic fragments of the lumen, circum- 
scribed by the inner skin, shrink to a curved, wavy, faintly yellow 
tube. This soon breaks up and disintegrates by degrees into a 
granular mass. Similar phenomena are also observed after plac- 
ing in iodine and diluted sulpliuric acid. With the bast fibres of 
the lower part of the stalk, which are poor in albumen, there re- 
mains after steeping, a thin, sac-like skin, which faintly reminds 
one of the appearance that hemp shows. However, the foldings 
are not so pronounced by far, and a confusion of the fibres, with 
anything like accurate observation, may be put aside as impossible. 
As has been before mentioned, the flax fibre has always cer- 
tain accompanying constituent parts, which are of greatest import- 
ance for accurate identification. Valuable guiding elements are 
found in the form of epidermis fragments, with numerous slit-like 
openings, free from hair; and with coarser fibres in the form of 




Fig. 21. Transverse section nf a typical fiax-fibre from middle of 
stem (Pernau-flax) in zinc chloride iodide. Mag. 30OX. 

chaflf (the woody part, which by the technical method of treating 
the fibre cannot be entirely removed). Detailed information is 
found in the author's atlas — Mikrophotographischcr Atlas der 
technisch wichtigcn Fascrstoffe. (J. B. Obernetter, Munich, 
Schillerstrasse 20. ) 



30 



DETERMINATION OF COTTON AND LINEN 




Fig. 22. Two hemp fibres, after treatment with ammoniacal copper 
o.xide. Both fibers show a sac-like, much folded, inner 
skin. Mag. loox. 

Often with bleached fibres, only traces of the cuticle from the 
epidermis are found, which cover it in the form of a thin skin 
(perhaps 1-1.5). Along with this, moreover, the primary ar- 
rangement of epidermis cells may be clearly recognized. With 
zinc chloride iodide the epidermis part is colored yellow to yellow 
brown. With dew-retted flax fibres, numerous fungus-threads 
are also found which may be readily observed after the applica- 
tion of caustic potash or chloral hydrate. Most common are the 
fungus threads of one of the inost common fungi : Cladosporium 
herbarnm Lk. Water-retted flax shows this appearance only if 




Fig. 23. Cotton fibres while being steeped in ammoniacal copper 
oxide. Mag. lOOx. 



MICROSCOPIC TESTS 



31 



the stalk, after harvesting-, has undergone retting under bad at- 
mospheric conditions. The above-mentioned woody parts are so 
easily recognizable that their characteristics under the microscope 
are omitted here. As already said, they appear onlv in coarse and 
badly cleaned material (tow). 





'"■••'■^rf^!^*^^''^^ 



Fig. 24. Flax fibre while being steeped in ammoniacal copper 
oxide. Mag. loox. 



32 DETERMINATION OF COTTON AND LINEN 



Appendix 

In closing, I give the following summary of the reagents 
necessary for the execution of the described tests. Those marked 
* can best be obtained from a dealer in chemicals ; the remaining 
substances are always kept by a druggist. 

1. Olive oil. 

2. Madder tincture, procured by extracting madder roots 
with alcohol. 

*3. Cochineal tincture. 

*4. Fuchsin. 

*5. Methylen-blue. 

*6. Cyanin. 

7. 10 per cent copper sulphate solution. 

8. 10 per cent solution of potassium ferrocyanide. 

9. Concentrated sulphuric acid. 

10. Diluted sulphuric acid. Concentrated sulphuric acid is 
carefully mixed with a little water, until cotton which has been 
treated with iodine potassium iodide dissolves v^'ith intense blue 
color under microscopic observation. 

11. Ammonia. 

12. Iodine in potassium iodide. In a strongly concentrated 
potassium iodide solution, the iodine is dissolved with a ruby red 
color. 

*13. Zinc chloride iodide. 
14. Amnioniacal copper oxide. Copper shavings are cov- 
ered with concentrated ammonia and allowed to remain a half 
hour, with frequent shaking. On account of the ready decompo- 
sition of the liquid, it is best freshly prepared. 

*15. 40° Be sodium hydroxide solution. 



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